linux-ext4 - [PATCH v5 13/23] fanotify: Allow file handle encoding for unhashed events

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Message-Id: <20210804160612.3575505-14-krisman@collabora.com>
Date:   Wed,  4 Aug 2021 12:06:02 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     jack@...e.com, amir73il@...il.com
Cc:     djwong@...nel.org, tytso@....edu, david@...morbit.com,
        dhowells@...hat.com, khazhy@...gle.com,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-api@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH v5 13/23] fanotify: Allow file handle encoding for unhashed events

FAN_FS_ERROR will report a file handle, but it is a unhashed event.n
Allow passing a NULL hash to fanotify_encode_fh and avoid calculating
the hash if not needed.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 fs/notify/fanotify/fanotify.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index a015822e29d8..0d6ba218bc01 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -385,8 +385,12 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 	fh->type = type;
 	fh->len = fh_len;
 
-	/* Mix fh into event merge key */
-	*hash ^= fanotify_hash_fh(fh);
+	/*
+	 * Mix fh into event merge key.  Hash might be NULL in case of
+	 * unhashed FID events (i.e. FAN_FS_ERROR).
+	 */
+	if (hash)
+		*hash ^= fanotify_hash_fh(fh);
 
 	return FANOTIFY_FH_HDR_LEN + fh_len;
 
-- 
2.32.0